First of all, congratulations on two excellent choices. They're both solid schools that match well.
McGovern is in the TMC has tons of research opportunities (in the school + next to baylor, MD Anderson, Methodist). It's also cheaper as you can establish in-state residency after paying out of state for 1 year with 23K/yr IS tuition. They have great hospital to rotate thru. They are P/F for first 6 months then become graded for rest of preclinicals.
Not very familiar with U of Az Tucson other than knowing their tuition is nice for in-state and they match well.
If you don't get in-state tuition at Arizona, 100% McGovern. If you're in-state Arizona, consider where your support is, what lifestyle you'd like (Houston v. Tucson), and how you'd do in each respective curricula. Best of luck!